Deputy Assistant Commissioner Neil Basu, senior national coordinator for UK Counter Terrorism Policing, said: "We still believe that Masood acted alone on the day and there is no information or intelligence to suggest there are further attacks planned."

But while he added that police "need to establish with absolute clarity why he did these unspeakable acts", DAC Basu acknowledged "there is a possibility we will never understand why he did this".

"That understanding may have died with him," he added.

He continued: "Nevertheless, we are determined to understand if Masood was a lone actor inspired by terrorist propaganda or if others have encouraged, supported or directed him.